By virtue of the progress in information communication networks and the like such as the Internet in these few years, each user can now easily access network information through individual-oriented terminals employing a cellular phone or the like.
In such information communication, information is transmitted through digital signals. It is now possible to obtain copied music and video information transmitted via the aforementioned information communication network without degradation in the audio quality and picture quality of the copy data, even in the case where an individual user performs the copy.
Thus, there is a possibility of the copyright of the copyright owner being significantly infringed unless some appropriate measures to protect copyrights are taken when any content data subject to copyright protection such as music data and image data is to be transmitted on the information communication network.
However, if copyright protection is given top priority so that distribution of content data through the disseminating digital information communication network is suppressed, the copyright owner who can essentially collect a predetermined copyright royalty for copies of a copyrighted work will also incur some disbenefit.
Instead of the distribution over the digital information communication network described above, distribution may be performed via record mediums storing digital data. In connection with the latter case, music data stored in CDs (compact disks) on the market can be freely copied in principle into magneto-optical disks (e.g., MDs) as long as the duplication is only for the personal use. However, a personal user performing digital recording or the like indirectly pays predetermined amounts in prices of the digital recording device itself and the medium as guaranty moneys to a copyright holder.
However, the music data is digital data, which does not cause deterioration of information when it is copied as digital signals from a CD to an MD. Therefore, for the copyright protection, such structures are employed that the music information cannot be copied as digital data from the recordable MD to another music data.
Under present circumstances, therefore, digital data can be freely copied from a CD to an MD, i.e., from a master of digital record medium to a slave, but cannot be copied from a recordable MD to another MD.
In view of the above, the public distribution itself of the music data and image data over the digital information communication network is restricted by the public transmission right of the copyright holder, and therefore sufficient measures must be taken for the copyright protection.
For the above case, it is naturally necessary to inhibit such an act that a user, who is not originally authorized, receives copyrighted data distributed to the public over the information communication network. Further, it is necessary to inhibit such an act that copyrighted data, which was once received by an authorized user, is further duplicated without authorization.